(module downstroke/renderer
    *
  (import scheme
          (chicken base)
          (only srfi-1 iota for-each)
          (prefix sdl2 "sdl2:")
          (prefix sdl2-ttf "ttf:")
          downstroke/entity
          downstroke/tilemap
          downstroke/world)

  ;; --- Pure functions (no SDL2, testable) ---

  ;; Returns (x y w h) as a plain list — testable without SDL2
  (define (entity-screen-coords entity camera)
    (list (- (inexact->exact (floor (entity-ref entity #:x 0))) (camera-x camera))
          (- (inexact->exact (floor (entity-ref entity #:y 0))) (camera-y camera))
          (inexact->exact (floor (entity-ref entity #:width 0)))
          (inexact->exact (floor (entity-ref entity #:height 0)))))

  ;; Returns sdl2:rect for actual drawing
  (define (entity->screen-rect entity camera)
    (apply sdl2:make-rect (entity-screen-coords entity camera)))

  ;; Returns flip list based on #:facing field
  (define (entity-flip entity)
    (if (= (entity-ref entity #:facing 1) -1) '(horizontal) '()))

  ;; --- Tilemap drawing ---

  (define (draw-tile renderer camera tileset tileset-texture tile-id row-num col-num)
    (let ((tile (tileset-tile tileset tile-id)))
      (sdl2:render-copy! renderer tileset-texture
                         (tile-rect tile)
                         (sdl2:make-rect
                           (- (* col-num (tileset-tilewidth  tileset)) (camera-x camera))
                           (- (* row-num (tileset-tileheight tileset)) (camera-y camera))
                           (tileset-tilewidth  tileset)
                           (tileset-tileheight tileset)))))

  (define (draw-tilemap-rows draw-fn rows row-num)
    (unless (null? rows)
      (for-each
        (cut draw-fn <> row-num <>)
        (car rows)
        (iota (length (car rows))))
      (draw-tilemap-rows draw-fn (cdr rows) (+ row-num 1))))

  (define (draw-tilemap renderer camera tileset-texture tilemap)
    (let ((map-layers (tilemap-layers tilemap))
          (tileset    (tilemap-tileset tilemap)))
      (for-each
        (lambda (layer)
          (draw-tilemap-rows
            (cut draw-tile renderer camera tileset tileset-texture <> <> <>)
            (layer-map layer)
            0))
        map-layers)))

  ;; --- Entity drawing ---

  (define (draw-entity renderer camera tileset tileset-texture entity)
    (let ((tile-id (entity-ref entity #:tile-id #f)))
      (when tile-id
        (sdl2:render-copy-ex! renderer tileset-texture
                              (tile-rect (tileset-tile tileset tile-id))
                              (entity->screen-rect entity camera)
                              0.0
                              #f
                              (entity-flip entity)))))

  (define (draw-entities renderer camera tileset tileset-texture entities)
    (for-each
      (lambda (e) (draw-entity renderer camera tileset tileset-texture e))
      entities))

  ;; --- Text drawing ---

  (define (draw-ui-text renderer font text color x y)
    (let* ((surface (ttf:render-text-solid font text color))
           (texture (sdl2:create-texture-from-surface renderer surface))
           (dims    (call-with-values (lambda () (ttf:size-utf8 font text)) cons))
           (w (car dims))
           (h (cdr dims)))
      (sdl2:render-copy! renderer texture #f
                         (sdl2:make-rect x y w h))))

  ;; --- Scene drawing ---

  (define (render-scene! renderer scene)
    (let ((camera          (scene-camera scene))
          (tilemap         (scene-tilemap scene))
          (tileset-texture (scene-tileset-texture scene))
          (tileset         (tilemap-tileset (scene-tilemap scene)))
          (entities        (scene-entities scene)))
      (draw-tilemap renderer camera tileset-texture tilemap)
      (draw-entities renderer camera tileset tileset-texture entities)))

) ;; end module renderer